This invention generally relates to intravascular catheters for treating a portion of a body lumen with radiation and particularly to a rapid exchange type intravascular catheter suitable for delivering a radiation source to the body lumen which utilizes a reinforcing mandrel to improve the pushability, strength and trackability of the catheter as it moves along a guide wire.
In percutaneous transluminal coronary angioplasty (PTCA) procedures, a guiding catheter having a preshaped distal tip is percutaneously introduced into the cardiovascular system of a patient through the brachial or femoral artery and is advanced therein until the preshaped distal tip is disposed within the aorta adjacent to the ostium of the desired coronary artery. The guiding catheter is then twisted and torqued from its proximal end to turn its distal tip so that it can be guided into the coronary ostium. In an over-the-wire dilatation catheter system, a guide wire and a dilatation catheter having an inflatable balloon on the distal end thereof are introduced into, and advanced through, the proximal end of the guiding catheter to the distal tip of the guiding catheter seated within the coronary ostium. The distal tip of the guide wire is usually manually shaped (i.e. curved) by the physician or one of the attendants before it and the dilatation catheter are introduced into the guiding catheter. The guide wire is usually first advanced out of the distal end of the guiding catheter and is maneuvered into the patient's coronary vasculature containing the stenosis to be dilated, and is then advanced beyond the stenosis. Thereafter, the dilatation catheter is advanced over the guide wire until the dilatation balloon is positioned across the stenosis. Once the dilatation catheter is in position, the balloon of the catheter is filled with radiopaque liquid at relatively high pressures (e.g., generally about 4-18 atmospheres) to inflate it to a predetermined size (preferably the same as the normal inner diameter of the artery at that particular location) in order to radially expand the lumen at the stenosis, thereby increasing the effective diameter of the occluded artery. The balloon can then be deflated so that the catheter can be removed and blood flow resumed through the dilated artery.
A rapid exchange type catheter has a relatively short guide wire-receiving sleeve or inner lumen (sometimes referred to as "rail") extending a short distance through the distal portion of the catheter body. This inner lumen preferably extends approximately 10 cm, and typically about 30 to 40 cm, from a first guide wire port at the distal end of the catheter to a second side guide wire port located on the catheter body. In some catheters, the "rail" can be much smaller than 10 cm, especially when the side guide wire port is located distal to the inflation balloon. The catheter can be advanced within the patient's vascular system in much the same fashion as described above as the short, inner sleeve of the catheter slides along the length of the guide wire. Alternatively, the guide wire may be first advanced within the patient's vasculature until the distal end of the guide wire extends distally to the stenosis with the catheter then being mounted onto the proximal end of the in-place guide wire and advanced over the guide wire until the balloon portion is positioned across the stenosis. This particular structure allows for the rapid exchange of the catheter usually without the need for an exchange wire or adding a guide wire extension to the proximal end of the guide wire. Other over-the-wire or rapid exchange catheters can also be designed to utilize therapeutic or diagnostic means in place of the balloon in the description above.
One common problem that sometimes occurs after an angioplasty procedure has been performed is the development of restenosis at, or near, the original site of the stenosis. When restenosis occurs, a second angioplasty procedure or even bypass surgery may be required, depending upon the degree of restenosis. In order to prevent the need to perform bypass surgery or subsequent angioplasty procedures, various devices and procedures have been developed for reducing the likelihood of development of restenosis after arterial intervention. For example, an expandable tube (commonly termed "stent") designed for long term implantation with the body lumen has been utilized to help prevent restenosis. By way of example, several stent devices and methods can be found in commonly assigned and commonly owned U.S. Pat. No. 5,158,548 (Lau et al.); U.S. Pat. No. 5,242,399 (Lau et al.); U.S. Pat. No. 5,344,426 (Lau et al.); U.S. Pat. No. 5,421,955 (Lau et al.); U.S. Pat. No. 5,514,154 (Lau et al.); and U.S. Pat. No. 5,360,401 (Turnlund et al.), which are incorporated in their entirety herein.
More recent devices and procedures for preventing restenosis after arterial intervention employ the use of a radiation source to minimize or eliminate proliferation of cells which is thought to be a major factor in the restenotic process. Balloon catheters have been suggested as a means to deliver and maintain the radiation source in the area where arterial intervention has taken place, exposing the area to a sufficient radiation dose to abate cell proliferation. Two devices and methods are described in International Publication No. WO 93/04735 (Hess) and WO 95/19807 (Weinberger). Other devices and methods which utilize radiation treatment delivered by an intravascular catheter are disclosed in commonly-owned and assigned co-pending U.S. Ser. No. 08/654,698, filed May 29, 1996, now abandoned entitled Radiation-Emitting Flow-Through Temporary Stent, which is incorporated herein by reference. Another medical device for the treatment of a body lumen by radiation is disclosed in European Patent App. 0 688 580 A1 (Schneider).
In the Schneider device, the balloon catheter includes a lumen that extends from a proximal opening to an area near the distal end of the catheter, where it "dead ends." This lumen, known as a "blind" or "dead end" lumen, is intended to carry a radioactive tipped source wire that slides into the lumen once the catheter is in place in the artery or body lumen. When the source wire is positioned, the radioactive section at the distal tip lies near the dead end to provide radiation to the body lumen.
The balloon catheter in the Schneider reference utilizes rapid exchange technology in which the catheter has a distal end guide wire port and a side guide wire port distal to the balloon portion of the catheter. This allows for rapid advancement and replacement of the catheter along the guide wire. Since the length of catheter which glides along the guide wire is relatively short, problems in shaft rigidity and tracking through tortuous, distal arteries can be encountered.
What has been needed and heretofore unavailable in catheters which provide treatment of the body lumen with a radiation source is an intravascular catheter which utilizes rapid exchange technology and has small transverse dimensions, yet provides adequate pushability and trackability for advancement deep into the patient's coronary arteries and across tight stenoses. Such an intravascular catheter would have to be relatively easy and inexpensive to manufacture. Additionally, the radiation source which is to be utilized should be protected from any contact with the patient's bodily fluids, so as to afford multiple use. An additional potential need is to provide blood perfusion distal of the lesion during the radiation process. The present invention fulfills these and other needs.